Report - PEER - University of California, Berkeley

the use of such connections in earthquake resistant steel frames, but it is important torecognize that there is a potential resistance to seismic actions. Even after rupture ofbolts on the weaker side, connections (and frames) can sustain further earthquakeshocks acting as rigid in one and as pinned in the other direction. Stiffness of framesis decreased in this case but a collapse does not occur as long as the resistance is notreached also on the stronger side of a connection. An existing three story industrialbuilding suffered rupture of bolts at the weaker side of two connections but theoverall behavior of the frame was not affected importantly.5. TIMBER-FRAME BUILDINGSIn light-frame buildings, shear walls are typically composed of wood framing andpanel sheathing attached with dowel-type fasteners, usually nails. The dowel-typemechanical connections are performing in an inelastic manner. Consequently, thebehavior of timber-frame wall panels to varying loads is inelastic. Deformability ofshear wall reflects in elastic deformation of sheathing material and framing membersand inelastic deformation of fasteners. For modeling the displacement response ofshear wall it is very important to develop an accurate model for the orthotropicinelastic behavior of fasteners in wood materials.5.1 Numerical ModelA two-step macro model for the calculation of the entire wood structure response hasbeen developed (Fig. 16). Within the first step (cyclic analysis) each singlewoodframe wall is numerically analyzed on the basis of the known inelastic behaviorof fasteners. The result of analysis is a hysteretic response of the wall. Based on thisresult, mechanical characteristics of inelastic spring that simulates the behavior of aphysical body – woodframe wall are derived. In the second step of the analysis(dynamic analysis) the entire building structure is simulated with inelastic springssimulating load-bearing walls. The model is supported by two different softwarepackages, i.e., DRAIN-2DX and CANNY-E. The results of two-dimensional analysesperformed by DRAIN-2DX are used for the composition of three-dimensionalstructural model suitable for the prediction of response of analyzed wood framedbuilding. Three-dimensional analysis is performed by CANNY-E program.To model both, structural connectors and equivalent structural struts, an element,called ULS (Universal Longitudinal Spring) has been developed. The physical modelis a longitudinal spring with appropriate length down to infinitely short dimension.The model had been originally developed for the modeling of masonry infill ofreinforced concrete frames (Žarnić 1994) and later modified for the simulation ofinelastic response of nailed sheathing to framing connections (Dujič and Žarnić2003). It applies significantly modified hysteretic rules proposed by the authors of theIDARC program (Park et al. 1987) and original skeleton curve with ductility and303